The present disclosure relates to a thermoplastic resin composition for three-dimensional printer filaments, and more particularly, to a thermoplastic resin composition for three-dimensional printer filaments applicable as a three-dimensional printing material requiring low hardness and soft feeling.
A three-dimensional (3D) printer is an apparatus for manufacturing a 3D shape by spraying inks with specific materials including a powder type one by one and laminating thereof to minute thicknesses. The utilization of 3D printing is being diffused into diverse fields. Particularly, a medical dummy capable of replacing a part of the body receives much attention, and the 3D printer is used for the manufacture of various shapes including toys and household objects such as kitchen supplies as well as automobiles including many parts.
Currently, a photocurable polymer material, i.e., a “photopolymer” which is cured on receiving light is the most widely used material for 3D printing. This material is widely used to such an extent as to occupy about 56% of the whole market and has advantages of having a rapid curing rate and forming a hard product, however has defects of hard recycling and high price. The following popular material is thermoplastic with a solid state of which melting and hardening are free. The thermoplastic occupies about 40% of the whole market, and a metal powder is expected to gradually increase a growing rate from now on. A thermoplastic material may be a filament type, a particle type or a powder type. 3D printing of the filament type is faster than other types and has high productivity and a fast diffusion rate.
As an existing filament material, polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), high density polyethylene (HDPE), polycarbonate (PC), etc. are used, and the reasons are as follows. First, the melting point thereof is suitably high, and a hardening rate after printing is rapid. Thus, with an increased printing rate, modification may not be generated, and dimensional stability and shape stability may be good. Second, since the melting point is suitably low, extrusion is easy and production efficiency is high during manufacturing filaments. Further, in the case that the melting point is too high, power consumption for melting filaments is high, and parts in a printer should be manufactured using a material enduring high temperature, thereby causing unnecessary increase of production costs.
Materials satisfying the above-mentioned diverse conditions include the above-mentioned four kinds, and all of these are materials having high hardness with greater than or equal to about Shore D50. Thus, the requirements of 3D printing materials of low hardness and soft feeling could not be satisfied. A 3D printed product using a material with low hardness and soft feeling may be applied to, for example, artificial skin, artificial joint, prostheses capable of replacing a part of the body used in medical field. Thus, the development of a novel material is required.
Meanwhile, polypropylene may be classified as isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and atactic polypropylene (aPP). Among them, studies on iPP and sPP are conducted due to good mechanical properties and thermal properties thereof, however commercial development of aPP is delayed due to the limitation of physical properties due to random stereoregularity. aPP may be separated as by-products during recovering an aliphatic solvent in an initial slurry process for preparing iPP, or may be prepared as a heterogeneous catalyst using modified titanium chloride(III) and an organoaluminum compound such as diethyl aluminum chloride as a co-catalyst or activator. However, in an iPP process with improved isotacticity, noncrystalline aPP is not produced as by-products any more. Although PP with low crystallinity is produced according to the object, aPP may be obtained by adding a comonomer.
By using a metallocene catalyst system, uniform aPP with narrow molecular weight distribution from high molecular weight to low molecular weight and high activity may be obtained via the structural change of a catalyst. In addition, the physical properties of aPP are largely affected by the molecular weight. Since aPP with low molecular weight has a sticky state without shapes at room temperature and has limitations in using, the molecular weight of about 150,000 and more is required. Although aPP obtained in the above catalyst system has high molecular weight, the polymerization activity thereof is very low, or polymerization results obtained at a relatively low temperature (less than or equal to 20° C.) to obtain high molecular weight are shown. Under the background, the present applicant suggested a method of preparing aPP with high molecular weight with high activity via propylene single polymerization using a catalyst composition including a novel transition metal compound having thiophene-fused cyclopentadienyl in Korean Patent Application No. 2011-0033626.